resolve hostnames : ds5 connections over ecom

[keith]

It would be nice if you had an option to enter a hostname
in the link setup when using a ecom.  There is no way
to use DNS to establish a connection.  (I.E. sorter.myname.com
instead of 192.168.1.4)

[BobO]

Yeah, that's one of those things we kick around from time to time. There are a couple of reasons we haven't pursued such things, but none of them are real killers. In general, we are not fond of using dynamic anything in a control environment; there are so many ways that can go wrong.

The original ECOMs didn't generate any traffic by themselves, so other than a TCP/IP address, there really wasn't much to configure or go wrong. With the addition of the report-by-exception feature, email, and the Modbus/TCP mastering, we had to add new configuration options. We tossed in DHCP about the same time. Of course all of these represent new and innovative ways to mess things up. 

That said, that is a great idea and something we'll definitely add to the wish list.

Thanks for the feedback.

[MikeS]

what behavior would you expect from the ECOM100 if it couldn't find it's DNS server? specifically, what impact should it have on the PLC system operation? none? some? user-defined?

[keith]

My application does not require the ECOM to find the DNS server.  Only the
DS32 software has to find the DNS server.

I don't realy plan to use DHCP.  My control network is fixed and static.

The place I would like to use the dynamic IPs is with remote access to
the system.  Our Cisco firewall forwards a public IP to the local IP's using
NAT.

Our real issue is that the public IPs change from time to time.
(particularly when our customers switch internet service providers).

Another usefull application is with a simple LINKSYS DSL router.  The newer
routers have TZO support, so even with a dynamic IP from your ISP, you can
get a hostname such as myname.tzo.com mapped to it. Then, you set the linksys
router to use NAT to map UDP port 28784 to your PLC's local IP address.  As far as the
ECOM is concerned, the IP is 192.168.1.1.  But to access it remotely, you use
myname.tzo.com in the DS5 software.

All these applications require changes to the DS5 alone.  The
H2ECOM can be left alone, as is (with static IP allocation).
I would do this as a first step.

Later, you could extend it even further by addressing the dynamic
DHCP issues, and the what-if issues of the server being down.

Keith

[BobO]

Ahh...my bad...

I looked right over the DS5 reference and got stuck on the ECOM part. It would be easy to add that to DS5...or DS6 perhaps.

Might still be cool to have the ECOM itself be able to resolve addresses, for many good reasons. But as Mike was alluding to, that also complicates error handling.

Again, thanks for the input.

[marksji]

I'll second this motion.  DS5 should resolve host names.  It really isn't a big deal, but I can map IPs in the DNS server and get guys to remember host names a lot easier than I get them to remember IP addresses.